Colorado Floods: What Happens to All That Water?

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As flood waters slowly begin to recede from central Colorado, new
flood warnings have cropped up downstream in Nebraska.

Colorado's South Platte River, which runs northeast from the
middle of the state into the southwest corner of Nebraska, has
taken the burden of much of the record
rainwater that hasn't already seeped into the ground.

A surge in the river began approaching the Nebraska border at
about midnight last night (Sept. 17), according to Dave Nettles,
an engineer with the Colorado Division of Water Resources, but
the crest of the surge had not yet reached the border as of this
morning. The crest will likely arrive today, Nettles said, but
the exact timing remains uncertain. [ Colorado
Flood Photos: 100-Year-Storm ]

The intensity of flooding is expected to be less severe in
Nebraska than it was in Colorado, since a portion of the water
has already seeped into ground aquifers, and because no new water
has been added to the system in the last couple of days, said
Robert Kimbrough, a hydrologist for the U.S. Geological Survey in
Denver.

Nebraska's relatively flat landscape also makes it less prone to
flooding than mountainous regions of Colorado, because streambeds
are wider and can handle more water there.

"The channels are pretty permeable and wide in Nebraska, so it
won't be like it is in mountainous regions like Colorado, where
there is less space for water and the water just goes up," said
Vitaly Zlotnik, a hydrogeologist at the University of
Nebraska-Lincoln.

As early as last Friday (Sept. 13), Colorado water officials
correctly predicted that floods would reach Nebraska today, and
warned Nebraska officials accordingly. The National Weather
Service has issued a series of flood warnings in the Southwest
region of the state, and predicts minor
to moderate flooding for the remainder of the week.

The South Platte River flows into Nebraska's Platte River, which
flows eastward along the southern half of the state. The river
widens as it gets further from Colorado, and will thus be able to
better accommodate the surge further into the state. Any water
that breaches the river thereafter will likely seep into
groundwater aquifers, and the rest will run eastward and
eventually flow into the Missouri River.